This invention pertains to a fiber optic interconnect system and, in particular, a multiterminator (MT) parallel optical interconnect system.
In lightwave communications, an optical transmitting device such as a laser or LED is connected to an optical fiber by directly butting the fiber to the active device, using lenses or mirrors to collect light from the laser or LED for transfer to the next stage, or by using an intermediate lightguide mechanism to collect the light from an active device and guide it to the fiber and take the light from the fiber for guiding it to the device which is to receive the optical data. Where a multifiber connector is used and the active device includes an array of optical fibers, an intermediate ferrule is typically used to align and mate the active sending device to a connector installed at the end of the optical fiber connector. The active device may be a light sending or receiving means. A ferrule is a block of plastic or glass with minute holes or light pipes extending through the block for conducting light from one end of the block to the other. The minute holes or light pipes of the light guide are intended to align optical fibers of ferrules in devices which are to be mated for transfer of optical data.
Optical fiber connectors having multiple fibers are known in the art. Such multi-fiber connectors are increasingly necessary as greater bandwidth applications are needed.
Multifiber connectors such as that in U.S. Pat. No. 5,214,730 show optical fiber ferrules formed by a pair of multifiber optical connector plugs having spring members for pressing the plugs toward each other in a direction axial to direction of ribbon cable inserted into the connectors. Guide pins are generally employed for aligning the multifiber optical connector plugs in an attempt to mate the ends of the individual fibers in arrays of optical fibers against one another to ensure good optical coupling, and hence effective transmission.
Generally, the array of fibers are mounted in V-grooves (U.S. Pat. No. 4,753,515) which are etched in a silicon material in order to provide for precision positioning of the fibers. Precision positioning of the fibers in the silicon block is imperative so that when two connectors are mated, the fibers align as closely as possible in order to limit any signal loss.
A typical fiber optic connector ferrule is shown in from U.S. Pat. No. 5,809,191, Stevens et al. It shows a single molded piece ferrule for receiving a multifiber cable of ribbon to provide at an open face of the ferrule having holes through which optical fibers pass. Guide pins extend parallel to one another from the ferrule for insertion into another ferrule for receiving guide pins in guide pin recesses.
Etched V-grooves can be put down with good precision, but it is difficult to bond them together and polishing them is also problematic. This results in a terminated ferrule having brittle surfaces and edges.
Another solution to alignment of optical fibers is shown in U.S. Pat. No. 5,664,039 by Grindersiev, where an array of optical fibers is held in grooves in a ferrule, and then these fibers are clamped into grooves with a second flat (ungrooved) ferrule member so fibers can be held precisely in the grooves. According to Grindersiev, this allows transmission through the connector with minimal fiber misalignment, since grooves hold the fibers securely. Grindersiev also teaches other means for optimizing data transmission by using various designs for securing fibers in grooves through alternative designs of groovesxe2x80x94V-shaped, semicircular, etc.
Another method for improving alignment of optical fibers in an MT style ferrule is shown in Shiflett, U.S. Pat. No. 5,619,604. It teaches a guide prong for pre-alignment of the ferrule within a receptacle and a groove on that guide prong for mating with a rib of the receptacle.
There exists a long felt need in the art for fiber optic connectors which achieves the result of machining with high precision and accuracy in the submicron range to hold individual fibers of a fiber optic array in registration with both a ferrule in which its ribbon cable is inserted as well as a ferrule to which it will be mated with aligning guide pins.
The prior art (for example, Grindersiev) teaches improving alignment of optical fibers in two optical connectors through improvement of alignment of the fibers within a single ferrule. Other prior art solutions, Shiflett, U.S. Pat. No. 5,619,604, solve the problem of ferrule alignment by adding mechanisms to the ferrule; this not only increases the cost and complexity of a connector, but also adds an opportunity for error in the machining of additional components, such as those taught in Shiflett, U.S. Pat. No. 5,619,604.
A prudent solution to the problem of aligning optical fibers in connecting MT ferrules has evaded the prior art, but would be very beneficial to the fiber optic industry.
It is an object of the present invention to provide a multiple terminator ferrule which both provides grooves for holding optical fibers in an MT ferrule while eliminating common errors in the manufacturing of grooved ferrules.
According to the present invention, a fiberoptic MT style ferrule includes hermaphroditic halves which are L-shaped insofar as they have perpendicular legs, one leg of each L-shaped ferrule halve having parallel elongate V-grooves at a mating end and a recess at a fiber-receiving end, the other leg of each L-shaped ferrule halve constituting a wall and having a guide pin hole parallel to said grooves, the hole providing alignment of the ferrule to alignment members, or guide pins, of another MT ferrule such that when the halves are bonded together, the grooves and recesses overlap in order that ribbon cable received in an opening formed by the overlapping recesses, continues into optical fibers within said overlapping grooves which can emanate from said mating end for optical data transfer to another ferrule.
The ferrule accommodates multiple fibers. The ferrule is injection molded plastic having grooves therein for receiving optical fibers. The ferrule is terminated by inserting multiple optical fibers within grooves of the ferrule and securing the optical fibers within the grooves via chemical bonding and polishing the end face of the ferrule. The ferrule is formed of two halves each having a major surface having V-grooves therein and the halves each having a pair of walls including holes for alignment guide pins. The ferrule includes a mating end and a rear end having a collar mounted thereon. The ferrule halves are bonded together and the fibers are secured therein via adhesive.
One advantage of the presently invented ferrule is that its hermaphroditic design lessens manufacturing costs because its ferrule halves are identical. A further advantage, which flows from the first, is that the effect on the function of the ferrule of variations in the manufacture of a first half of the ferrule are minimized because the other half of the ferrule has the same variation, but positioned in the opposite direction with the result that the variations in the halves complement each other. For example, if two ferrules A and B are to be mated, each of A, B will be comprised of identical halves. Thus, ferrule A has a top half and bottom half and ferrule B has a top half and bottom half, and all four halves are identical. If the top half of manufactured ferrule A has a groove at location xe2x80x98xxe2x80x99, whereas the groove was designed for location xe2x80x98y,xe2x80x99 this irregularity will be matched by the same irregularity if any in the top half of a ferrule Bxe2x80x94with which ferrule A would mate.
The prior art, in which a ferrule is made of a single molded piece having guide pin holes and holes for optical fibers, would not circumvent this error. In the prior art MT ferrule, a number of core pins equal to the eventual number of optical fibers to be enclosed by this ferrule are then inserted into this single molded piece for creating the holes for the fibers. The problem with this approach, solved by the present invention, is that each iteration of the core pin insertion is different from the prior iteration such that no two iterations produce the same ferrule. The error leads to two ferrules which are to be mated but which may have fibers that are misaligned. In the course of manufacturing perhaps a hundred thousand ferrules, the room for error is large.
According to the invention, differences between a designed ferrule part the manufactured actual ferrule are less likely to lead to a faulty mating of ferrules, even if there is a manufacturing irregularity in the ferrule. Moreover, differences between successive batches of manufactured ferrules will all function correctly and identically even if those successive batches produce non-identical ferrule halves.
These and other features of the invention are set forth below in the following detailed description of the presently preferred embodiments.